Why this happens

Think of Java fonts like a toolbox

Without overriding:

Java uses logical fonts ("Dialog", "SansSerif") that internally map to multiple physical fonts — they support fallback.

Text: Hello 🌟 世界

Java:

• "Hello" → Noto Sans
• "🌟" → Emoji font
• "世界" → Noto CJK

Everything renders properly.

When you override the font:

You’re telling Java:

Use ONLY this one font. Don’t fall back to anything else.

So if the font doesn’t have emoji or CJK characters → they break.

Font font = new Font("Noto Sans", Font.PLAIN, 20);

Text: Hello 🌟 世界

Java:

• "Hello" → Noto Sans
• "🌟" → missing → []
• "世界" → missing → []

Solution Options

Option 1: Use a logical font instead

Option 2: Set component fonts individually (selectively apply)

Option 3: Composite font via Font.createFont() (Advanced)